Session: Thursday Morning, June 19

Time: 10:55

Consider the meridional plane which contains the axis of a circular
cylinder and the incident acoustic wave vector. The meridional leaky rays which
lie in this plane may be excited for certain tilt angles. Radiation resulting
from the reflection of such rays off truncations on a cylinder gives strong
high-frequency backscattering enhancements [Kaduchak et al., J. Acoust. Soc. Am.
100, 67--71 (1996)]. The present work gives ray approximations for such
backscattering contributions and for the related contributions to scattering by
tilted infinite cylinders. These are evaluated using a general convolution
integral formulation [P. L. Marston, J. Acoust. Soc. Am. 100, 2820(A) (1996)].
The infinite cylinder results for radiation by Rayleigh waves on a solid
cylinder agree with the partial-wave series solution. The truncation enhancement
for a finite cylinder causes a backward-directed three-dimensional wavefront
possessing a vanishing Gaussian curvature. The amplitude from the far-field
propagation integral associated with the caustic due to this wavefront can
significantly exceed the amplitude for reflection off a rigid sphere having the
same radius as the cylinder. The analysis does not rely on thin shell
assumptions. [Work supported by the Office of Naval Research.]